Hi all We've been surveying a cave from half way between two entrances, and working outwards towards those entrances over a number of survey trips. As each survey trip has been completed, I have been drawing, and constructing an extended centreline, and attaching scraps. The extended centreline is just a little bit complicated, with two loops, but I have managed to get the breaks where I want them, and offset passages to lay it out nicely. As each centreline is added, I modify the extend left and right for that survey to suit the extended centreline shape that I want. I have 'anchored' the downstream entrance with a dummy survey leg, until I surveyed downstream to that entrance and I could remove the dummy leg. I have 'extended right' to the downstream entrance. All has gone well until I surveyed out of the upstream entrance, extending left, mostly. But as soon as I add a station flag to the upstream entrance, the shape of the extended centreline is broken. It looks like Therion is overriding the 'extend start' that I have in the middle of the cave, and replacing it with a start at the top entrance. This completely scrambles the shape of the centreline and attached scrap drawings. It looks a bit like the default behaviour listed here <https://survex.com/docs/manual/extend.htm> (the first paragraph of the main text) for Survex. I have tried a few approaches to avoid this undesirable behaviour, but nothing yet has worked. I would rather not try to recreate the extend development from upstream, as Therion seems to want me to do, because even with such a simple cave, there is some complexity and time involved in figuring it out. Good, but no upstream entrance flag Bad, after adding upstream entrance flag the extends are broken station 4.24 "Top Entrance" entrance Any suggestions? Bruce
